Differential measurements of the elliptic ($v_2$) and hexadecapole ($v_4$) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum ($p_T$) and collision centrality or number of participant nucleons ($N_{\mathrm{part}}$) for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The $v_{2,4}$ measurements at pseudorapidity $|\eta |\le 0.35$, obtained with four separate reaction-plane detectors positioned in the range $1.0<|\eta |<3.9$, show good agreement, indicating the absence of significant $\Delta \eta$-dependent nonflow correlations. Sizable values for $v_4(p_T)$ are observed with a ratio $v_4(p_T,N_{\mathrm{part}})/v_2^2(p_T,N_{\mathrm{part}})\approx 0.8$ for $50\lesssim N_{\mathrm{part}}\lesssim 200$, which is compatible with the combined effects of a finite viscosity and initial eccentricity fluctuations. For $N_{\mathrm{part}}\gtrsim 200$ this ratio increases up to 1.7 in the most central collisions.

• Received 29 March 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.062301